The k-based cyclic neutron activation analysis ( k-CNAA) technique has been studied to explore the applicability at the Portuguese research reactor (RPI). In particular, for the determination of elements which form short-lived radionuclides, particularly fluorine (F, 11.16 s half-life) and selenium (Se, 17.36 s half-life) in polymer, biological and environmental samples. The detection limits obtained for F and Se were about 50 and 0.01 mg kg, respectively, in the investigated materials. The timing parameters for the procedure were 10 to 20 s for irradiation, 5 s decay, 10 to 20 s counting, 5 s waiting and performed with eight cycles. The k-IAEA program was modified to use millisecond time resolution for irradiation, decay and counting times as needed for interpreting k-CNAA data in terms of concentration, accuracy and detection limit. The quality control of the procedure was performed by preparing a standard solution containing fluorine with different contents as well as using the certified reference materials containing selenium from which the bias between the results and the certified values were within 15% for most elements at the investigated content ranges. The analytical results for several other elements producing short-lived or detectable radionuclides, e.g., Al, Ca, Cl, Cu, Dy, I, Mg, Mn, Ti, and V were also obtained by the k-CNAA procedure with accuracy within 12%.

Three new synthetic multi-element standards (SMELS) were developed for testing the performance of the k0-standardization neutron activation analysis (k0-NAA) method when implemented in a laboratory. SMELS consist of a phenol-formaldehyde polymer matrix spiked with different groups of elements...

The theoretical and practical aspects of the use of radioactive daughters originated from the decay of longer-lived radioactive mothers in parametric activation analysis, when the ratio: mother half-life to daughter half-life is less than 10, are discussed. The mother-daughter relationships:...

The combination and optimization of the cyclic modes in neutron activation analysis (NAA) at the Dalat research reactor were performed to determine short-lived nuclides. This work focused on determination of selenium in biological materials using Se ( T = 17.4 s) as a case in point. The...

A fast pneumatic transfer facility was installed in Nuclear Engineering Teaching Laboratory (NETL) of the University of Texas at Austin for the purpose of cyclic thermal and epithermal neutron activation analysis. In this study efforts were focused on the evaluation of cyclic epithermal neutron...

The determination of Zn in geological samples using instrumental neutron activation analysis is usually done using the Zn(n,Î³)Zn reaction and its 244 day half-life. However this analysis has proven to be potentially difficult. This is due to its relatively low neutron absorption cross section...

For the Î²+-decay of 22Na in the metallic environment Pd cooled to T = 12 K the 22Na half-life was observed to be shorter by 1.2Â±0.2%. The result is consistent with --but lower than-- the prediction of the Debye plasma model.

Since the initial determination of the Q and k factors for Se systematic errors in Se determination in various matrices have been noticed by several users of the k method. A number of publications have been made on this subject, resulting in different k and Q values for this radio-isotope. This...